CNC Internal Grinding Spindles Outer Diameter: 150 mm Max. Speed: 12,000 rpm Bearing Lubrication: Grease Bearing size: Ø30 Ø45 Power: 8 kW Kenturn has been designing, manufacturing, fabricating and marketing machine tool spindles of all kinds since 1983. The company prides itself on intensively studying spindle design and producing innovative technology.